CX3CR1 and neoplasm: In healthy human donors, in vivo administration of granulocyte colony-stimulating factor (G-CSF) enhanced the expression of CD62L and CXCR4 on the surface of NK cells in peripheral blood.256 TGF-β, an important immunosuppressive factor in the TME, increased the expression of CXCR4, CX3CR1, and CXCR3 on NK cells in vitro.257 This enhancement may potentially promote the egress of NK cells from the TME and represents a novel mechanism for tumor escape.